Solenoid-operated electric switch



March 13, 1956 E. F. REIHMAN 2,738,395

SOLENOID-OPERATED ELECTRIC SWITCH Filed Nov. 22, 1952 Inventor: Ear! F. Reih ah,

His Attor y.

United States Patent 2,738,395 SOLENOID-OPERATED ELECTRIC SWITCH Earl F. Reihman, Fairfield, Conn., assignor to General Electric Company, a corporation of New York Application November 22, 1952, Serial No. 322,055

6 Claims. (Cl. 200-112) The present invention relates to solenoid-operated electric switches and particularly to switches of this type used in connection with remote control wiring systems for house and similar installations. In such installations, the electric circuit for the solenoid winding or windings is of low voltage, for example of the order of 24 volts, and it may be controlled by simple low voltage switches of the pushbutton type; and the relay switch which is actuated by the solenoid controls the power circuit, for example, an electric light circuit which is of higher voltage, in the case of a house wiring system a voltage of the order of 120 volts.

Solenoid-operated electric switches for this type are required to be small so they may be used in connection with standard house wiring outlet boxes which means that the solenoid is small and limited in strength.

The object of the present invention is to provide in connection with a main solenoid operated electric switch an auxiliary switch which may be used, for example, for controlling a pilot light circuit for the solenoid-operated switch to indicate its position, which auxiliary switch is simple in structure; requires negligible energy for its operation; is small and compact so that it adds little to the size of the overall switch structure, and can be incorporated into the switch structure at low cost.

According to my invention I provide a solenoid-operated switch structure wherein the solenoid is mounted at one end on the top wall of the main switch casing and has one end of its plunger or armature connected to the movable member of the main switch; and wherein at the other end of the solenoid there is provided an enclosing cap in which is housed an auxiliary switch, the movable member of which is connected to the other end of the solenoid plunger. In its preferred form the auxiliary switch comprises walls forming a mercury chamber and a contact pin which is connected to the solenoid plunger and projects through an opening in the mercury chamber wall and is moved by the plunger into and out of contact with the mercury, the opening through which the pin projects being so small that mercury will not flow into it.

For a consideration of what I believe to be novel and my invention, attention is directed to the following specifications and to the claims appended thereto.

In the drawing,

Fig. 1 is a sectional view of a solenoid-operated switch structure embodying my invention.

Fig. 2 is a sectional view taken at right angles to that of Fig. 1.

Fig. 3 is a wiring diagram illustrating the manner in which the switch structure may be connected into a remote control system.

Referring to the drawing, 1 indicates a main switch housing on the bottom wall of which are fixed contacts 2 for connection to a main circuit. In the housing is a movable contact member 3 for bridging contacts 2 to close a circuit through them.

Mounted on the top wall 4 of housing 1 is a solenoid comprising a spool having two windings 5 and 6 thereon. The spool comprises at its outer or upper end a metal disk 7 and at its inner or lower end a metal disk 8 and an insulating disk 9, the disks being held by a tubular sleeve 10 of non-magnetic material such as brass, the ends of which are flanged out over the disks as indicated at 11. Sleeve 10 forms the center of the spool structure. Surrounding the coil structure is an outer casing 12 having a flange 13 at its lower end which rests on the outer portion of disk 8 and through which and the disk 3 and 9 extend one or more rivets 14 for fastening the solenoid to main switch casing 1.

Positioned in and guided by sleeve 10 is a solenoid armature or plunger which comprises a strip 15 of insulating material to opposite sides of which are attached metal strips 16 by means of rivets 17. At its lower or inner end insulating strip 15 projects beyond strips 16 and through an opening in top casing wall 4 into switch casing 1 and the end is attached to contact member 3 by a harp spring 13 attached to strip 15 by an eyelet 19. Contact member 3 may be of any suitable type, the specific structure forming no part of the present invention. The essential thing is that it is moved into and out of engagement with contacts 2 by axial movement of the armature or plunger. In the present instance it is shown as comprising a known type of over-center spring strip contact similar to that disclosed in the patent to Hausler, 2,332,911, patented October 26, 1943, which is assigned to the same assignee as the instant application. Axial movement of the plunger or armature in each direction is limited by spaced stops 20 attached to strip 15 by eyelet 19 which engage a disk 21 fixed in the switch hous ing by a screw 22. Upward movement of the solenoid plunger to close the switch as shown in full lines in Figs. 1 and 2 is limited by lower stop 20 engaging the under side of disk 21, and downward movement of the plunger to open the switch is limited by upper stop 20 engaging the top of disk 21. The open position of over-center spring strip contact member 3 is shown in dotted lines in Fig. 1, its movement being limited by stops 23 formed on housing 1.

In use in a remote control wiring system, switch housing 1 is located inside the outlet box, the solenoid proecting to the outside of the box through a knockout open ing. For holding the structure in the box, casing 12 is provided on opposed sides with tapered spring strips 24 which may be formed from material of the casing and which at their ends adjacent to switch casing 1 are shaped to provide recesses 25 in which the edge wall of a knockout opening may be positioned. Thus in assembling the structure in an outlet box, the solenoid is pushed through an outlet box knochout opening from the inside of the box, strips 24 yielding inwardly as they press against the edge of the knockout opening and then springing out when their lower ends pass beyond the box wall so that the edge of the knockout opening rests in recesses 25. Figs. 1 and 2 show the structure on an enlarged scale. As built, casing 12 would have an outside diameter just slightly less than the diameter of an outlet box knockout opening. From this it will be clear that the solenoid is small; also that the throw of the solenoid plunger is small. For example the throw may be of the order of .020 of an inch. This requires that an auxiliary switch to be built into or as a part of the structure must not only be small and require negligible energy for its operation but also that it must be operated between open and closed positions by the small plunger throw available. In addition it should be a switch which may be used in any angular position.

The auxiliary switch comprises a switch housing in the form of a cap 31 formed preferably of insulating material which is fastened over the outer end of the solenoid by an inturned flange 32 on the upper end of casing 12 which rests on an annular shoulder on cap 3-1. Inside cap 31 is a dome-shape housing 33 of suitable metal integral with which is a tubular stem 3d which projects out through a metallic bushing 35 fixed in the top wall of cap 31. Stem 34 is threaded, having threaded engagement with bushing 35, and on its outer end it is provided with a notch to receive a tool for adjusting the position of the housing in the cap. On theouter end of stem 34 is a nut 36 for use in attaching a lead wire to housing 33. The bore of stein 34 is sealed by a plug 37. Hons ing 33 has a bottom wall 38 formed from insulating material held in place by a flange 39 on casing 33. In bottom wall 38 is a small opening 49 in which slides a contact pin 41 having a pointed inner end. The outer or lower end of pin 41 is electrically and mechanically connected between the upper ends of strip 16 by a ball and socket joint as shown at 42 Housing 33 is filled with mercury as indicated at 43 which may be passed into the housing through stem 34 and sealed therein by plug 37. Pin

4-1 is of a length such that in one position of the solenoid plunger its pointed end projects beyond bottom wall 38 into contact with mercury 43 as shown in full lines in Fig. 1, and in the other position of the plunger, the pointed end is drawn down into opening 4% as shown in dotted lines in Fig. 1. Opening 50 is so small in diameter that mercury will not flow into it. Contact pin 41 may to advantage be formed from stainless steel coated with silicone to prevent adhesion of mercury to it. The inner side of wall 38 where pin 41 passes through it is provided with a projection 44 so that the end of the pin contacts with the mercury above the inner surface of the wall and well into the mercury mass. This serves to insure contact even when the switch is positioned with the solenoid pointing downward.

One terminal of the mercury switch is the stem 34. The other terminal is pin 41 which is grounded through solenoid plunger strips 16, sleeve 10, disk 8 and casing 12, and to insure good contact between strips 16 and sleeve 10 a spring strip 45 of suitable material is positioned between one or both of the strips 16 and sleeve 10 to frictionally connect them.

When a solenoid plunger is in the position shown in Figs. 1 and 2, the main switch being closed, the auxiliary switch is closed also, the pointed end of pin 40 being in the mercury 4-3. When the solenoid plunger moves to open the main switch as indicated in dotted lines in Fig. l, the pointed end of pin 41 is drawn down into opening 40 out of contact with the mercury. This requires but a short movement of the plunger and the moving of the pin requires negligible force. It will be understood that the solenoid windings 5 and 6 are provided with suitable lead wires (not shown) which are connected to the windings and may extend out through the outer end of cap 31'.

Fig. 3 shows diagrammatically the switch structure of Figs. 1 and 2 connected into a remote-controlled wiring system. Solenoid windings 5 and 6 are connected through pushbutton switches 46 and 47 to the secondary of a step-down transformer .8 which has its primary connected to a power line indicated at 49. The main switch has its contacts 2 connected to power line 49, the connections including the circuit load here indicated as an electric lamp 5%. The auxiliary circuit switch has its terminals connected across the secondary of the stepdown transformer, the connections including a pilot light 51. Pilot light 51 may be located adjacent to pushbutton switches 47 and will indicate whether the main switch is open or closed.

The closing of push button switch 46 closes a circuit through solenoid winding 5 to move the solenoid plunger in a direction to close the main switch and the auxiliary tsh The d n f pus b t witch 7 lo a ite h u h o no wi d 6 t m th so enoi plunger in a direction to open the mainlswitch and the auxiliary switch. Only a momentary closing of the pushbutton switches is needed to effect operation of the main and auxiliary switches by the solenoid.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A mercury switch comprising a metallic casing having a thick wall portion formed from insulating material, a mass of mercury filling said casing, said wall having an elongated opening through it so small that mercury will not flow into it, a raised projection portion on the inner face or" said wall surrounding said opening and being in abutting engagement with the mercury, a contact pin supported in and guided by said opening, and means connected to said pin for moving it in said opening to bring its end into and out of contact with the mercury in the casing.

2. In combination, a pair of electric switches operated by a single solenoid therebetween comprising a main switch at one end of the solenoid having switch contacts and a movable switch member, a plunger for the solenoid, and an insulating strip connecting the said plunger to said movable switch member, and an auxiliary mercury switch supported at the opposite end of said solenoid and comprising a two-piece hollow housing, the outermost portion of the housing being a terminal contact means of electrical conductive material while the innermost portion of the housing is of thick insulating material and is provided with an elongated hole substantially in alignment with the longitudinal axis of said plunger, said hole being of such size that when the housing is tilled with mercury the surface tension of the mercury will prevent the egress of the mercury through said hole, and an auxiliary switch contact comprising a pin supported in said opening and connected to the other end of said plunger, said pin being of such a length that movement of the plunger to operate the main switch moves the pin in said opening to bring its end into and out of contact with the mercury in said housing, the said pin and plunger serving as a circuit connection for the mercury switch.

3. in a structure as recited in claim 2, wherein the said auxiliary mercury switch is adjustably supported at one end of the solenoid so that the reciprocating movement of the plunger will move the pin into and out of the mercury to operate the auxiliary switch.

4. In a structure as recited in claim 2, wherein the electrical connection from said contact pin includes a conducting spring strip mounted on said plunger to be in sliding engagement with a conducting sleeve which defines the opening through the solenoid through which the plunger extends.

5. In a structure as recited in claim 2, wherein the contact pin is connected to said plunger by means of a universal connection.

6. In combination, a main switch housing, switch contacts and a movable switch member in the housing, a solenoid having one end supported on one of the walls of said housing, a plunger for the solenoid, an opening in said solenoid supporting wall of the housing, and an insulating strip within said opening and connecting said plunger with said movable switch member, an outer metallic casing for said solenoid, and a cap mounted on the other end of the solenoid for supporting an auxiliary mercury switch therein, said mercury switch comprising a two-piece hollow housing, the outermost portion extending through said cap and constituting a first terminal contact means of electrical conductive material while the innermost portion of the said latter housing is of thick insulating material and is provided with a small elongated hole substantially in alignment with the longitudinal axis of said plunger, said hole being of such a size that when the housing is filled with mercury the surface tension of the mercury will prevent the egress of the mercury through said hole, and an auxiliary switch contact comprising a pin supported in and guided by said opening and connected to the other end of said plunger,

said pin being of such a length that movement of the 1,289,637 Bruce, Jr. Dec. 31, 1918 plunger to operate the main switch moves the pin in 1,648,100 Aichele Nov. 8, 1927 said opening to bring its end nto and out of contact with 2,000,136 Huss May 7, 1935 the mercury, the said pin being electrically grounded 2,136,874 Bartsch Nov. 15, 1938 through the plunger and through a conducting spring 5 2,415,448 Stilwell, Jr. Feb. 11, 1947 strip mounted on said plunger to be in sliding engagement 2,544,719 OBrien et al. Mar. 13, 1951 with a conducting sleeve which defines the opening 2,545,629 Posey et a1 Mar. 20, 1951 through the solenoid through which the plunger extends, and finally through the casing of the solenoid to provide FOREIGN PATENTS the second terminal means for said auxiliary mercury 10 205,374 Switzerland 1, 1939 Switch 247,686 Germany June 5, 1912 607,862 Germany Jan. 9, 1935 References Cited in the file of this patent UNITED STATES PATENTS 882,340 Palmer Mar. 11, 1908 15 

